Let's say due to politics and war the Cold War by 1970 was effectively the US, Western Europe, ANZ and Japan against the rest of the world. The scenario does not matter and neither does the issue of military security; this PC is purely upon the question of the following:
Is an economically isolated West viable? If the capitalist system only comprised of North America, Western Europe, ANZ and Japan(+ maybe South Africa, Israel), and trade effectively only went around these countries, would it survive? (Implied question: do they not need "poorer" countries to keep inflation at check and keep production low-cost?)